Plasma spraying ZrB 2 ceramic coating is considered as potential candidate method of Thermal Protective System. While the application of plasma sprayed ZrB 2 coating is restricted due to its oxidation. Therefore, it is important to study the oxidation behavior of the ZrB 2 material. In this research, oxidation behavior of the ZrB 2 ceramic, which achieve different density by using SPS and pressureless sintering, is studied to explain the oxidation behavior of plasma spraying ZrB 2 ceramic coating. The oxidation behavior of ZrB 2 ceramics is investigated using SEM, XRD and EDS. The ZrB 2 –based ceramic coating is gravely oxidized at 600°C, but the block ZrB 2 –based ceramics also possess excellent oxidation resistance above 1000°C. The density of ZrB 2 ceramics significantly increase when changing the sintering method from pressureless sintering to SPS. The high density has beneficial effect to improve the oxidation resistance of ZrB 2 ceramic, for there are few open pores channel in high density ceramics. The oxygen cannot diffuse to the inner through pores, as a result, the high density ceramics can only be oxidized from outside to inside progressively, unlike low density ceramics, whose surface and inner is oxidized simultaneously.

In this paper, nanostructure Lanthanum zirconate thermal barrier coatings (MCrAlY+ La 2 Zr 2 O 7 ) were prepared by atmospheric plasma sprayed (APS). The microstructures and thermal stability properties were systematically studied by Scanning Electric Microscopy (SEM), transmission electron microscope (TEM) and X-Ray diffraction(XRD). The results showed that the nanostructured lanthanum zirconate coatings were typical lamellar structure which was composed of columnar grains about 90nm in diameter. A large quantity of micro-cracks and homogeneous distributed fine pores formed in the nanostructured zirconia coating. After ablation at 1300 °C for 24 h, no apparent phase transformation was observed in lanthanum zirconate coating. The growth mechanism of the grains was subsequently discussed.